1. Field of the Invention
The present invention relates to a bearing apparatus, a spindle motor, and a disk drive apparatus.
2. Description of the Related Art
Spindle motors arranged to rotate disks are typically installed in hard disk apparatuses and optical disk apparatuses. Such a spindle motor includes a stationary portion fixed to a housing of the apparatus, and a rotating portion arranged to rotate while supporting the disk(s). The spindle motor is arranged to generate a torque centered on a central axis through magnetic flux generated between the stationary portion and the rotating portion, so that the rotating portion is caused to rotate with respect to the stationary portion.
A fluid dynamic bearing apparatus, for example, is used as a bearing apparatus to support the rotating portion such that the rotating portion is rotatable with respect to the stationary portion. A known spindle motor including a fluid dynamic bearing apparatus is described in, for example, JP-A 2004-270820.
The fluid dynamic bearing apparatus includes a dynamic pressure generation portion in which a dynamic pressure groove is defined in a member of a stationary portion or a member of a rotating portion. Accordingly, once the rotating portion starts rotating, a dynamic pressure is generated in a fluid arranged between the member of the stationary portion and the member of the rotating portion. This produces a supporting force that supports the rotating portion with respect to the stationary portion. In the fluid dynamic bearing apparatus as described above, an air bubble may be introduced into the fluid, or an air bubble may be generated in the fluid due to a change in pressure on the fluid, while the rotating portion is rotating. If any air bubble stays in the vicinity of the dynamic pressure generation portion, the dynamic pressure generated in the dynamic pressure generation portion may become unstable.